The invention relates to a preparation method of a near-infrared long afterglow luminescent nanometer particle. The near-infrared long lasting phosphorescent nanometer particle is prepared by adopting a mesoporous silica template method. The preparation method of the near-infrared long afterglow luminescent nanometer particle comprises the steps of firstly preparing mesoporous silica through a hydrothermal method; then adopting the silica as a carrier, adopting gallium and germanium zinc glycinate as a base material, uniformly stirring with a mixed solution codoped by chromium ions and rare earth ions, centrifugally separating, drying at the temperature of 80 DEG C, and carbonizing through a muffle furnace at the temperature of 550 DEG C; then using a sodium hydroxide solution for dissolving and removing a silica template in a sample, centrifugally separating a product once again, drying at the temperature of 80 DEG C, and finally calcining through the muffle furnace at the temperature of 700 DEG C; and preparing the near-infrared long afterglow luminescent nanometer particle with the average grain diameter being less than 10 nanometers. The preparation method of the near-infrared long afterglow luminescent nanometer particle provided by the invention has the advantages that the near-infrared long afterglow luminescent nanometer particle prepared by the method has excellent properties that the grain size is controllable, the grain diameter is smaller, an emission spectrum is within a near-infrared light area, the afterglow time is long, and the like; and the preparation method of the near-infrared long afterglow luminescent nanometer particle provided by the invention is simple to operate and low in cost, does not require reducing atmosphere during a preparation process, and has no pollution on the environment.